Buying an Oscilloscope

[anatech]

Hi star882,
Agilent is HP, the test equipment division.

I'm interested in why you think the quality is down ... ahhhh, you're talking about their computers! No relation to the test equipment division at all. If you want to see really low quality, look at ECS products or Emachines. Total scrap.

I've played with Agilents new stuff. Absolutely lovely equipment. Having also played with new Tek, LeCroy and others in the same time period, I feel I can justify my comments. For me, an MSO6000 series machine (four channels would be nice) at about 500 MHz would satisfy what I need from a 'scope. I'd love more, but the prices rapidly escalate past the price of a nice new car. I can't afford any of it, so this is all but a pipe dream.

I did pick up a non-functional HP 1722A. 275 MHz, two channel. I'm looking forward to checking this thing out once I get it operating. I hear they don't trigger well, but we'll see. I also have a broken Tek 468, so if I can fix both .... I'll better understand what the gripes are all about.

With costs for DSP solutions, memory and improvements to A/D converters and op amps, the newer 'scopes are packing a ton of performance into a small box. For my money though, you will need an analog 'scope as well until the resolution of DSOs gets better. Most are only 8 bit vertical with some special modes at 12 bit vertical resolution. Don't expect a 16 bit solution, and from what I've been able to find out, most analog systems are really only good to about 14 bits of resolution once noise and other factors are considered.

-Chris

[stratus46]

Originally Posted by anatech

Just to add,
Absolutely everything I have purchased off Eeekbay has been broken or not functional in some way, even guarantied good units. Shipping back across the border from Canada is a no flier after paying duties and brokerage fees.

For something like a primary 'scope, I'll buy new only. It's okay to buy secondary 'scopes used. Assume there is something wrong. Even if the picture is very good. (oops, we must have shipped the wrong one).

Pay attention to the brands and model numbers! Old Tek scopes have no real support, and newer there is poor access to parts and information. Philips have terrible reliability problems (I have one from new, PM series). HP stuff is better for information and access to parts. Old ones require donor units. I find that the HP stuff has a much higher build quality over most other units.

Pay attention how hot a unit runs. Philips "combi" scopes run hot as do parts of the PM 30xx series. New Tek units (DPO4000) run stinking hot somewhere - I will not touch one for that reason alone. Watch the size. Some older 'scope systems are huge, possibly making your power meter spin. The newer DPO4000 series from Tek is larger than your average scope (ie: it may not fit where you want to put it).

-Chris

I've bought several video cards, motherboards, 3 Technics receivers, 8 Metcal soldering irons and many tips, 2 Fluke meters and a frequency counter, 3 ATI HDTV Wonder tuner cards and more. 1 Metcal power unit was bad and needed an IRF130 to make it work but I only paid $10 for it. I guess my luck is better than others.

If money wasn't object I'd have Tek 3054 scope but those go for $11600. You might want to check out the Rigol digital scopes. I'll stick with my Tek 475A

G²

[anatech]

Hi G²,
I have had a demo Rigol 'scope here for a week. It's better than what I thought it might be, but nowhere as good as the other 'scopes I have tried. Your luck is far, far better than mine.

There is another issue to think about as well when buying test equipment. When you buy something like an Agilent product, you get about the most reliable product on the market. They also hold their calibration exceptionally well. These two points are actually far more important than you might consider. 10 years go by almost without notice. We expect the test equipment to actually last about 20 years - and for the most part, they have lasted 20 years or longer.

With this in mind, I'm very picky when it comes to placing money on the table. For example ... the Tektronix 'scope I used on demo has a noisy and clearly audible fan noise when it runs at higher speeds. Can you imagine what your bench would sound like with this and other fan cooled equipment. I know understand why test equipment was often installed in 18" rack cabinets with no missing panels. To cut the noise level down. But on a more serious note, I measured the air exhaust to be a full 20 °C warmer than the inlet air. Something is running pretty darn hot in there. My current Philips PM-3070 has died four times so far, simply due to excessive temperatures. The same PCB every time.

Avoid buying anything with a clear problem. Also understand that elevated temperatures will cause components to age far more quickly and calibration to drift. The LeCroy 'scope I tried ran warm, but not as warm as the Tek. The two Agilent models I tried ran far cooler, and the 6000 series 'scope had a similar profile to an analog 'scope (meaning it fits on my bench), and a fan that was not something I noticed.

To be honest, most analog 'scopes are reliable. They will also do most of what we ask of them. DSOs are cool looking, have nifty features and so forth, but they do not behave just like an analog 'scope. Some of the controls are a pain to get to as well with the newer DSOs. You'll find them in menus for the "soft keys" or on a multifunction control. Not user friendly at all. The easiest ones to use were the LeCroy and the Agilent DSOs.

The Tek 475 is supposed to be one of the better 'scopes I've heard. One day I may get a chance to try one. These older Tek units probably represent the best choice for a DIY enthusiast. Just make sure it actually works.

-Chris

[gtforme00]

Star has a little trouble with context, but is otherwise an impressive bot. Her older posts on the refrigeration forums were so incoherent they were amusing, but "she" seems to have evolved greatly since then.

-David

[quietdragon]

Originally Posted by star882

I believe HP sold their oscilloscope division to Agilent so hardware should not be a problem. Firmware bugs are definitely annoying, though.

For those interested in the history, HP divested itself of the Test and Measurement section of the company in 2000. That divested portion was spun off as a brand new company and was named Agilent. The HP name stayed with the computer products part of the company.

[anatech]

Hi quietdragon,
Yes. Most anyone you talk to considers that the HP name should have stayed with the test and measurement division. The name had considerable brand recognition and a strong tie to the idea of quality. The current computer products company has been eroding the "good will" that the original brand had earned itself over the decades of supplying excellent test and measurement products.

So far, Agilent is doing far better with it's reputation than HP is. It's sad to see a mark that stood for quality be ground down by en endeavor unrelated to the original corporate activities. HP only began selling computers to run automated test programs, they were not originally considered for public use at all. Now they are a "value brand" not much better than most others, "e-machines" being the cheap junk they've inflicted on us all. I have to admit that I like their better printers and multifunction machines.

Very few software bugs are allowed out with Agilent. They are very pro-active when it comes to the equipment they sell. The Infinium line is interesting as they run on the windows platform. You can even run other apps and surf the web. I have to say I'm disappointed they aren't running some flavor of Linux nicely nailed down. Far more reliable OS that doesn't require so much memory. Come to think of it, Linux doesn't leak memory like Windows still does (or the apps - I don't care which does it.).

-Chris